1. Field of the Invention
The present invention relates to a boron doped p-type single crystal silicon carbide semiconductor and a process for preparing the same.
2. Descriptions of the Related Art
Doping boron, a III-group element, as an acceptor has been done in an attempt to form a p-type silicon carbide semiconductor. Specifically, boron is added during crystal growth of silicon carbide or boron is introduced in a single crystal silicon carbide by ion implantation, to obtain a p-type single crystal silicon carbide semiconductor.
Nevertheless, it was difficult to obtain a p-type silicon carbide semiconductor having a high carrier concentration and a high activation rate (see, for example, M. V. Rao et al.: Journal of Applied Physics Vol. 77, No. 6 (1995) p.2479). The reasons reported for this difficulty are: that the acceptor level of boron doped in silicon carbide is as deep as 735 meV based on the filled band (S. G. Bishop et al.: Amorphous and Crystalline Silicon Carbide edited by G. L. Haris et al., Springer-Verlag Berlin Heidelberg (1989) p.90), that the site of boron doped in silicon carbide is the site of carbon in a non-doped silicon carbide, i.e., the so-called carbon site (J. A. Freitas et al.: Amorphous and Crystalline Silicon Carbide edited by G. L. Haris et al., Springer-Verlag Berlin Heidelberg (1992) p.135), and so on.
Methods and procedures for controlling the carrier concentration in a boron-doped p-type silicon carbide are not known.
The object of the present invention is to increase the carrier concentration and the activation rate of a boron-doped p-type silicon carbide semiconductor.